Waste product streams containing primarily water, and smaller amounts of nonaqueous liquids and solids, both organic and inorganic, are by-products of the refining, petrochemical and chemical industries, to name a few. For example, a typical waste stream from a refinery operation will contain about 80 percent-by-weight water, about 15 percent-by-weight oil, e.g., hydrocarbons and other nonaqueous liquids, and about 5 percent-by-weight solids. Due to environmental regulations, these waste stream pose disposal problems.
It is known to treat a refinery waste stream, commonly referred to as sludge which is a mixture of solids, water and oil products, in such a manner to obtain either a solids stream which is a slurry of solids, both inorganic and organic, in a primarily aqueous medium, the slurry generally containing from about 15 to about 20 percent-by-weight solids content, or a non-pumpable dry solids cake. Such slurries, containing a relatively small amount, i.e., less than about 10 percent-by-weight, of nonaqueous liquids, e.g., hydrocarbons, can be incinerated as for example, in furnaces used in regenerative spent sulfuric acid plants, cement kilns or the like. These prior art aqueous slurries have several disadvantages. For one, because of the high water content, they have a low heat value. Additionally, the solids content of the slurries cannot exceed about 20-25 percent lest they become so viscous as to be unpumpable at ambient temperature conditions. Accordingly, the cost of disposing of the slurries is increased because the transportation costs per unit weight of solids is relatively high. In the case of non-pumpable, dry solids cake, the solids content is generally 25 to 90 percent-by-weight. This cake requires special handling for disposal and is considerably more expensive than the slurries to dispose of.